The sport of "free-falling" wherein a suitably-dressed participant jumps out of an aircraft and falls for a time in "free-fall" before opening a parachute is becoming increasing popular in the United States and in other countries. Recent reports indicate, surprisingly, that China has the largest number of free-fall enthusiasts of any country in the world. Quite apart from the sports aspects of such activity, the air forces of every militarily significant country require their paratroops and special forces to be trained in free-fall techniques.
It is obviously very expensive, and can be fatally dangerous, simply to take an untrained person and let them learn free-fall techniques only while dropping from an aircraft toward the ground. Therefore, there has long been a perceived need for a system providing an adequate cross-section of essentially uniform, i.e., linearized, air flow at a speed between 90 mph. to 150 mph. very close to the ground. With such a system, one or more trainees can be artificially maintained in simulated "free-fall" conditions at a safe height and in a manner which permits training staff to communicate with and correct trainee errors in real time.
Among the known systems is one taught in U.S. Pat. No. 5,209,702, titled "FREEFALL SIMULATOR", to Arenas, issued on May 11, 1993. It teaches a freefall simulator system housed in a building specifically designed for this purpose, and employs a hydraulic drive train consisting of two separate hydraulic motors, one to provide from 0% to 50% of the power needs of the simulator and the other to provide the remaining 51% to 100% of such power needs on a controlled increase, on demand, to drive a propeller to generate an upward air flow corresponding to the specific size, shape and weight of a person practicing simulated freefall. The building containing the system is deliberately designed for noise abatement, with an "earth berm" surrounding it to redirect any noise escaping the building in an upward direction. The system uses "S" shaped baffles mounted over large individual baffles disposed above a propeller rotated by the combined output of the two separate hydraulic motors.
The above-described system, like other earlier-developed known systems, requires an entire building, needs expensive and relatively complex drive systems, and has other related limitations.
After considerable research and development effort, it was determined that it is possible at reasonable power levels to generate a large, high-speed, linearized upward flow in an entirely open system to greatly facilitate simulated free-fall experiences by one or more participants, while allowing one or more trainers literally to stand within arms reach of the participants/trainees actually doing the simulated free-falling. The present invention is based on this theoretical and empirical development, and provides a sturdy system that can be erected and disassembled relatively quickly and economically, making it possible for a user, such as a military service, to provide training at short notice and to provide training in out-of-the-way places very conveniently. The invention also lends itself to forms suitable for general public participation, e.g., at fair grounds and the like.
The invention, as described below and as illustrated in the accompanying drawing figures, employs a very simple and rugged structure to efficiently linearize a substantial upward air flow, especially over the propeller axis, while simultaneously enabling both participants and trainers to safely walk at a suitable height above the air-flow generating propeller